diff --git a/idea/src/org/jetbrains/jet/plugin/highlighter/DebugInfoAnnotator.java b/idea/src/org/jetbrains/jet/plugin/highlighter/DebugInfoAnnotator.java
index 6c809d52de2..9c873a73df0 100644
--- a/idea/src/org/jetbrains/jet/plugin/highlighter/DebugInfoAnnotator.java
+++ b/idea/src/org/jetbrains/jet/plugin/highlighter/DebugInfoAnnotator.java
@@ -21,6 +21,7 @@ import com.intellij.lang.annotation.AnnotationHolder;
 import com.intellij.lang.annotation.Annotator;
 import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.progress.ProcessCanceledException;
+import com.intellij.openapi.roots.ProjectFileIndex;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.tree.TokenSet;
@@ -60,6 +61,9 @@ public class DebugInfoAnnotator implements Annotator {
         if (!isDebugInfoEnabled() || !JetPsiChecker.isErrorReportingEnabled()) {
             return;
         }
+        if (!ProjectFileIndex.SERVICE.getInstance(element.getProject()).isInContent(element.getContainingFile().getVirtualFile())) {
+            return;
+        }
         
         if (element instanceof JetFile) {
             JetFile file = (JetFile) element;
diff --git a/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java b/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java
index b44a532d3c7..3fcbddeae37 100644
--- a/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java
+++ b/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java
@@ -25,6 +25,7 @@ import com.intellij.lang.annotation.Annotator;
 import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.editor.colors.TextAttributesKey;
 import com.intellij.openapi.progress.ProcessCanceledException;
+import com.intellij.openapi.roots.ProjectFileIndex;
 import com.intellij.openapi.util.TextRange;
 import com.intellij.psi.MultiRangeReference;
 import com.intellij.psi.PsiElement;
@@ -104,7 +105,8 @@ public class JetPsiChecker implements Annotator {
             try {
                 BindingContext bindingContext = WholeProjectAnalyzerFacade.analyzeProjectWithCacheOnAFile(file).getBindingContext();
 
-                if (errorReportingEnabled) {
+                boolean isInContent = ProjectFileIndex.SERVICE.getInstance(element.getProject()).isInContent(file.getVirtualFile());
+                if (errorReportingEnabled && isInContent) {
                     Collection<Diagnostic> diagnostics = Sets.newLinkedHashSet(bindingContext.getDiagnostics());
                     Set<PsiElement> redeclarations = Sets.newHashSet();
                     for (Diagnostic diagnostic : diagnostics) {